OT stands for Occupational Therapy. It was an occupational therapist, A. Jean Ayres, who developed the theory of sensory integration (SI) and researched how sensory integration disorders impact on behaviors, task performance and higher level cognitive and perceptual skills. An SI trained OT is often the appropriate professional to consult when dealing with sensory integration disorder or what is now being referred to sensory processing disorder.
I think that the line IS blurred between OE and SPD. Sensory processing happens on a continuum and, like intellect, it is usually only the extreme ends that are different enough to be problematic. I really like Winnie Dunn's take on sensory processing: Living Sensationally: Understanding Your Senses is a great little read on the topic. Not OE oriented, it provides an overview of how sensory processing affects our behaviors.
